Continuous removal of cadmium and lead ions by biochar derived from date seeds in a packed column reactor

The ability of date seed-derived biochar (DSB) to remove cadmium(II) and lead(II) from single and multi-solute solutions in packed column have been investigated. These column trials were conducted to understand the effects of column parameters such as bed depths, initial Cd(II)/Pb(II) concentrations and flow rates. The results indicated that the metal uptake of DSB decreased with increase in flow rate, and decrease in initial metal concentration and bed depth values. At a flow rate of 0.3 L/h, bed height of 25 cm, and initial metal concentration of 1 mmol/L, DSB recorded maximum Cd(II) and Pb(II) uptake values of 0.525 and 0.462 mmol/g, respectively. The continuous adsorption data models such as Yoon–Nelson, Thomas, and modified dose-response equations were utilized. Multi-component column studies were also performed and the results indicated decreased uptake of Cd(II) and Pb(II) by DSB due to competition. At optimized conditions, DSB recorded 0.447 and 0.449 mmol/g for Cd(II) and Pb(II), respectively, in multi-solute system. The column elution and subsequent reuse of DSB for next cycle was possible with 0.01 M HCl as elutant. The column regeneration was attempted for three cycles and the results indicated that DSB produced consistently high Cd(II) and Pb(II) removal efficiencies and uptakes.